Thermal heating system and a controller for the same

Abstract

A system comprising a main circuit for routing a flow of heat transfer liquid out of a thermal storage to at least one outer heat exchanger and back to the thermal storage again, a main circulation pump configured to force the heat transfer liquid through the main circuit, a temperature sensor configured to measure the temperature of the heat transfer liquid, and a controller configured to control the main circulation pump based on temperature readings of the temperature sensor such that a calculated Reynolds number for the flow of heat transfer liquid is constant at a predetermined target Reynolds number over at least a primary temperature range.

The invention claimed is: 
     
       1. A geothermal heating and/or cooling system comprising:
 a geothermal storage; 
 at least one outer heat exchanger; 
 a main circuit configured to route a flow of heat transfer liquid out of the geothermal storage to the at least one outer heat exchanger and back to the geothermal storage again; 
 a main circulation pump configured to force the heat transfer liquid through the main circuit; 
 a temperature sensor configured to measure the temperature of the heat transfer liquid; 
 a flow rate sensor configured to measure flow rate in a return portion of the main circuit after the at least one outer heat exchanger; and 
 a controller configured to control the main circulation pump based on temperature readings of the temperature sensor such that a calculated Reynolds number for the flow of heat transfer liquid is constant at a predetermined target Reynolds number over at least a primary temperature range, wherein the predetermined target Reynolds number is within the range of 2500-3500 such that turbulent flow of the heat transfer liquid is achieved, 
 wherein the controller is configured to control a speed of the main circulation pump to achieve a target flow rate measured by the flow rate sensor in a return portion of the main circuit after the at least one outer heat exchanger, and 
 wherein the controller is further configured to base the control of the main circulation pump on a predetermined control curve, lookup table or function correlating temperature reading of the temperature sensor with target flow of heat transfer liquid for a given target Reynolds number. 
 
     
     
       2. The system according to  claim 1 , wherein the geothermal storage comprises a bore comprising a bore heat exchanger. 
     
     
       3. The system according to  claim 1 , wherein the main circulation pump is provided on a supply portion of the main circuit upstream of the at least one outer heat exchanger. 
     
     
       4. The system according to  claim 1 , wherein the temperature sensor is configured to measure temperature in a return portion of the main circuit downstream of the at least one outer heat exchanger. 
     
     
       5. The system according to  claim 1 , wherein the controller is further configured to limit the speed of the main circulation pump to an operating range defined by a bottom speed and a top speed. 
     
     
       6. The system according to  claim 5 , wherein the bottom speed is set such that a minimum flow rate of the main circuit is higher than a maximum total flow rate of the at least one outer heat exchanger. 
     
     
       7. The system according to  claim 1 , wherein the at least one outer heat exchanger is configured to deliver comfort heating. 
     
     
       8. The system according to  claim 1 , wherein the at least one outer heat exchanger is configured to deliver comfort cooling. 
     
     
       9. The system according to  claim 1 , wherein the at least one outer heat exchanger is configured to deliver cooling of an industrial process. 
     
     
       10. A controller configured to control a main circulation pump configured to force heat transfer liquid through a main circuit for routing a flow of heat transfer liquid out of a geothermal storage to at least one outer heat exchanger and back to the geothermal storage again, the controller comprising:
 a receiver configured to receive a temperature reading from a temperature sensor configured to measure the temperature of the heat transfer liquid of the main circuit; 
 a flow rate calculator configured to, based on the temperature reading, calculate a flow rate for the heat transfer liquid of the main circuit such that a calculated Reynolds number for the flow of heat transfer liquid is constant at a predetermined target Reynolds number over at least a primary temperature range, wherein the predetermined target Reynolds number is within the range of 2500-3500 such that turbulent flow of the heat transfer liquid is achieved; 
 a control signal generator configured to, based on the target flow rate, generate a control signal for the main circulation pump, the control signal comprising information pertaining to the calculated target flow rate at which the main circulation pump is to operate, wherein the control signal generator is further configured to base the generation of the control signal on a predetermined control curve, a lookup table or a function correlating the temperature reading with target flow rate of heat transfer liquid for a given target Reynolds number; and 
 a transmitter configured to send the control signal to the main circulation pump, wherein the receiver is further configured to receive a flow rate reading from a flow rate sensor configured to measure a flow rate in the main circuit, wherein the control signal generator is further configured to base the generation of the control signal on the flow rate reading. 
 
     
     
       11. A method for reducing power consumption and increasing heat transfer efficiency of a geothermal heating and/or cooling system comprising:
 a geothermal storage; 
 at least one outer heat exchanger; 
 a main circuit configured to route a flow of heat transfer liquid out of the geothermal storage to the at least one outer heat exchanger and back to the geothermal storage again; and 
 a main circulation pump configured to force the heat transfer liquid through the main circuit, the method comprising:
 measuring a temperature of the heat transfer liquid; 
 measuring a flow rate in a return portion of the main circuit after the at least one outer heat exchanger; 
 controlling the main circulation pump based on the measured temperature of the heat transfer liquid such that a calculated Reynolds number for the flow of heat transfer liquid is constant at a predetermined target Reynolds number over at least a primary temperature range, wherein the predetermined target Reynolds number is within the range of 2500-3500 such that turbulent flow of the heat transfer liquid is achieved; and 
 controlling a speed of the main circulation pump such that a target flow rate is achieved, 
 wherein the controlling of the main circulation pump is based on a predetermined control curve, lookup table or function correlating temperature reading of a temperature sensor with target flow of heat transfer liquid for a given target Reynolds number. 
 
 
     
     
       12. The method according to  claim 11 , wherein the temperature is measured in a return portion of the main circuit downstream of the at least one outer heat exchanger.